Techniques for importation of information to a storage system

ABSTRACT

Various embodiments are generally directed an apparatus and method for receiving an event notification for a pair of cluster nodes having a first cluster node and a second cluster node, the event notification indicating an occurrence of a takeover event or a giveback event. Further, various embodiments may include suspending copying of information from a source logical unit to a target logical unit, transferring one or more processes from the first cluster node to the second cluster node and resuming importation of information from the source logical unit to the target logical unit.

The present application claims the benefit of earlier filed ProvisionalU.S. Pat. App. No. 61/916,095, filed on Dec. 13, 2013, which isincorporated by reference herein in its entirety.

BACKGROUND

Data migration is the process of copying data or information from anexisting storage device to a new storage device. Migrating storage areanetwork (SAN) based data to different storage systems is an ongoingchallenge. For example, moving information using backup and restore froma tape device is slow and cumbersome and does not scale well. The resultis that data migration projects tend to be time consuming and costly,requiring extensive application downtime.

Many factors drive the need to migrate information from one storagesystem to another storage system. For example, storage systems may needto be upgraded for better performance and capacity or replaced when theycome off lease. Applications may need to move from test and developmentstorage systems to production storage systems. Disk distributions,Redundant Array of Independent Disks (RAID) groups, and so on arereorganized periodically as performance or protection needs change overtime. Thus, data migration is not a one-time challenge, but a recurringeffort that consumes time, resources, and budgets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary embodiment of a system overview of astorage computing system.

FIG. 1B illustrates a second exemplary embodiment of a system overviewof a storage computing system.

FIG. 2 illustrates a third embodiment of a storage computing systemhaving cluster nodes.

FIG. 3 illustrates an exemplary embodiment of hardware architecture of acluster node.

FIG. 4 illustrates an exemplary embodiment of a storage operating systemarchitecture.

FIGS. 5A/5B illustrate exemplary embodiments of storage computing systembound to a source logical unit and a target logical unit.

FIGS. 6A-C illustrate exemplary embodiments of a bounded storagecomputing system during takeover and giveback events.

FIG. 7 illustrates an exemplary embodiment of a logic flow.

FIG. 8 illustrates a second exemplary embodiment of a logic flow.

FIG. 9 illustrates an embodiment of a first computing architecture.

DETAILED DESCRIPTION

As previously discussed, current data migration from one storage system(source storage system) to another storage system (target storagesystem) is time consuming, costly and an ongoing challenge. Thus,various embodiments are generally directed towards data migration fromsource storage system to a target storage system and handling faults,failures, mobility events, takeover and giveback events, and the likeduring data migration.

In various embodiments, the source storage system and the target storagesystem may each have one or more storage devices and store informationas a logical unit, e.g., a source logical unit and a target logicalunit. Further, each of the storage systems may include one or morecluster nodes or controllers coupled with the storage devices to formthe storage system. In various embodiments, the cluster nodes may beseparate computing devices and or controllers for processing read/writerequests for the storage system.

The target storage system may be introduced into a preexisting storagesystem environment, such as a storage area network (SAN) environmentincluding the source storage system. The importation of information fromthe source storage system and source logical unit to the target storagesystem and target logical unit may be initialized. More specifically,the target logical unit may bind with the source logical unit throughone or more cluster nodes and information may be copied from the sourcelogical unit to the target logical unit on a block-by-block basis.

Some embodiments are directed to handling read and write requests from ahost device during the importation of information. As will becomeapparent in the follow description, read requests may be handled by thetarget storage system and serviced by the source logical unit. Morespecifically, the target storage system may process the read requestfrom the host device and read information from the source logical unitbased on the read request. Further, write requests from the host devicemay also be handled by the target storage system and serviced by thesource logical unit and the target logical unit. More specifically, thetarget storage system may process write requests by writing informationto the source logical unit and the target logical unit based on thewrite request. By processing the read and write requests from a hostdevice, the importation of information may be seamless and transparentto the host device. Moreover, a limited amount of downtime to accessinformation by the host device may be experienced during the importationof information.

Some embodiments may also be directed to handling failure, takeover andgiveback events experienced by a storage system. As previouslydiscussed, the storage systems may include one or more cluster nodes.For example, the target storage system may include four cluster nodeswhere each cluster node is paired with another cluster node to form twopaired cluster nodes. As will be discussed in more detail below, thepaired cluster nodes may form a high availability cluster node systemsuch that if one cluster node fails it's paired cluster node cantakeover processing from the failed cluster node. Further, a clusternode may giveback processing to its paired cluster node when it comesback online.

During a failure, takeover or giveback event, one or more modules orcomponents of the storage system may handle the event such that thefailure is transparent to a host device and the importation of data doesnot have to restart from the beginning. For example, when a cluster nodefails, the importation processing may stop or be suspended until thepaired cluster node assumes reasonability of the processes on the failedcluster node. In addition, any logical units associated with failedcluster node may be associated with the new cluster node, processesexecuting on the failed cluster node may be initialized and operate onthe paired cluster node and configuration information may be updated inmemory or a data store. More specifically, configuration oridentification information may be updated such that host deviceread/write requests are sent to the correct cluster node, the pairedcluster node is identified as the current cluster node handling theimportation processing and the location of the logical units associatedwith the paired cluster node is updated.

Once the paired cluster node has taken over processing and theconfiguration information is updated, the importation of information maybe restarted. In some embodiments, a checkpoint may be saved in thetarget logical unit after a region of information is copied from thesource logical unit to the target logical unit. Thus, in the case of afailure, takeover or giveback event, the importation process may restartfrom the last checkpoint saved in the target logical unit. These andother details will become more apparent in the following description.

With general reference to notations and nomenclature used herein, thedetailed description that follows may be presented in terms of programprocedures executed on a computer or network of computers. Theseprocedural descriptions and representations are used by those skilled inthe art to most effectively convey the substance of their work to othersskilled in the art.

A procedure described here is generally conceived to be aself-consistent sequence of operations leading to a desired result.These operations are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical, magnetic or optical signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It provesconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers, or the like. It should be noted, however, that all of these andsimilar terms are to be associated with the appropriate physicalquantities and are merely convenient labels applied to those quantities.

Further, the manipulations performed are often referred to in terms,such as adding or comparing, which are commonly associated with mentaloperations performed by a human operator. No such capability of a humanoperator is necessary, or desirable in most cases, in any of theoperations described herein that form part of one or more embodiments.Rather, the operations are machine operations. Useful machines forperforming operations of various embodiments include general-purposedigital computers or similar devices.

Various embodiments also relate to apparatus or systems for performingthese operations. This apparatus may be specially constructed for therequired purpose or it may include a general-purpose computer asselectively activated or reconfigured by a computer program stored inthe computer. The procedures presented herein are not inherently relatedto a particular computer or other apparatus. Various general-purposemachines may be used with programs written in accordance with theteachings herein, or it may prove convenient to construct morespecialized apparatus to perform the required method steps. The requiredstructure for a variety of these machines will appear from thedescription given.

FIG. 1 illustrates a general overview of an exemplary computing system100 including a host device 102, network 104 having one or moreinterconnects, a storage system 106 and a storage array 110 having oneor more storage devices 108. In various embodiments, computing system100 may be a clustered storage system in a storage area network (SAN)environment. For example and as will be discussed in more detail withrespect to FIGS. 2, 4A, 4B and 5A-5C, storage system 106 may include anynumber of cluster nodes.

Host device 102 may be any type of computing system configured toexecute one or more applications. Moreover, the host device 102 mayinteract with the storage system 106 in accordance with a client/servermodel of information delivery. That is, the host device 102 may requestthe services of the storage system 106, and the system may return theresults of the services requested by the host, by exchanging packetsover the network 104. The host device 102 may communicate packetsutilizing file-based access protocols, such as the Common Internet FileSystem (CIFS) protocol or Network File System (NFS) protocol, overTCP/IP when accessing information in the form of files and directories.In addition, the host device 102 may communicate packets utilizingblock-based access protocols, such as the Small Computer SystemsInterface (SCSI) protocol encapsulated over TCP (iSCSI) and SCSIencapsulated over Fibre Channel (FCP), when accessing information in theform of blocks.

In various embodiments, network 104 may include a point-to-pointconnection or a shared medium, such as a local area network. In the sameor other embodiments, network 104 may include any number of devices andinterconnects such that host 102 may communicate with storage system106. Illustratively, the computer network 104 may be embodied as anEthernet network, Fibre Channel (FC) network or any other type of mediumto communicate messages or information. The host 102 may communicatewith the storage system 106 over the network 104 by exchanging discreteframes or packets of data according to pre-defined protocols, such asthe Transmission Control Protocol/Internet Protocol (TCP/IP), aspreviously discussed.

Storage system 106 may be one or more computers or cluster nodes thatprovide storage services relating to the organization of information onstorage devices, such as storage devices 108. As will be discussed inmore detail below, storage system 106 may include any number of clusternodes having elements and components to provide storage services to host102 and other storage systems. More specifically, storage system 106 mayinclude a number of elements, components and modules to implement ahigh-level module, such as a file system, to logically organize theinformation as a hierarchical structure of directories, files andspecial types of files called virtual disks (vdisks) or logical unitsidentified by a logic unit number (LUN) on the storages devices 108.

In some embodiments, storages devices 108 may include hard disk drives(HDD) and direct access storage devices (DASD). In the same oralternative embodiments, the storage devices 108 may include electronicmedia, e.g., Flash memory, etc. As such, the illustrative description ofwriteable storage device media comprising magnetic media should be takenas exemplary only.

Storage of information on storage array 110 may be implemented as one ormore storage “volumes” that include a collection of storage devices 108cooperating to define an overall logical arrangement of volume blocknumber (vbn) space on the volume(s). The disks within a logicalvolume/file system are typically organized as one or more groups,wherein each group may be operated as a Redundant Array of Independent(or Inexpensive) Disks (RAID). Most RAID implementations, such as aRAID-4 level implementation, enhance the reliability/integrity of datastorage through the redundant writing of data “stripes” across a givennumber of physical disks in the RAID group, and the appropriate storingof parity information with respect to the striped data. An illustrativeexample of a RAID implementation is a RAID-4 level implementation,although it should be understood that other types and levels of RAIDimplementations may be used in accordance with the inventive principlesdescribed herein.

In some embodiments, the information on storage array 110 may beexported or sent to host 102 as one or more data structures such as alogical unit identified by logical unit numbers (LUNs). The LUN may beunique identifier used to designate individual or collections of harddisk devices for address by a protocol associated with a SCSI, iSCSI,Fibre Channel (FC), and so forth. Logical units are central to themanagement of block storage arrays shared over a storage area network(SAN). Each LUN identifies a specific logical unit, which may be a partof a hard disk drive, an entire hard disk or several hard disks in astorage device, for example. As such, a LUN could reference an entireRAID set, a single disk or partition, or multiple hard disks orpartitions. The logical unit is treated as if it is a single device andis identified by the LUN.

In some embodiments, the logical unit may be made up of a number of alogical blocks identified by logical block addresses. The logical blocksmay be of a particular size, such as 64 kilobytes (KB) or any othersize. Furthermore, each logical block address identifies one logicalblock of the particular size.

FIG. 1B illustrates a second illustrative embodiment of a computingsystem 150 having an additional storage system 152 and storage array 156having one or more storage devices 154. In various embodiments, storagesystem 152 may communicate with host 102 and storage system 106 vianetwork 104 over one or more interconnects, as previously discussedabove. In some embodiments, storage system 152 may be the same as orsimilar to storage system 106 and storage array 156 having storagedevices 154 may be the same as or similar as storage array 110 andstorage devices 108.

In various embodiments, storage system 152 and storage array 156 may beintroduced into the SAN environment and information from storage system106 and storage array 108 may be imported to storage system 152 andstorage array 156. As will become more apparent with the followingdescription, information stored in storage array 110 may be seamlesslyimported, copied or moved to storage array 156. Moreover, the importing,copying or moving of the information may be transparent to the hostdevice 102. In addition, once the information is imported from storagesystem 108 and storage array 110 to storage system 152 and storage array156, storage system 108 and storage array 110 may be transparentlyremoved from the computing system without the host device's 102knowledge.

FIG. 2 illustrates an embodiment of a computing system 200 including ahost device 202 connected or coupled with a storage system 206 in astorage area network (SAN) environment. In various embodiments, thestorage system 206 may be similar to or the same as storage systems 106and 152. FIG. 2 illustrates storage system 206 including cluster nodes204-1 through 204-4 coupled with storage devices 208-1 through 208-4.

Cluster nodes 204-1 through 204-4 may be any computing device includinga processor, processing circuitry, a controller, a storage controller,and so forth. Storage devices 208-1 through 208-4 may be the similar orthe same as storages devices 108 and 154. Although FIG. 2 onlyillustrates four cluster nodes and four storage devices, variousembodiments may include any number of cluster nodes and storagesdevices. Further, each cluster node may be coupled with more than onestorage device such as in a storage array configuration similar tostorage arrays 110 and 156.

The storage system 206 can make some or all of the storage space on themass storage devices 208 available to the host device 202. For example,the host device 202 can access a cluster node 204 of the storage system206 using well known protocols, such as Internet Small Computer SystemInterface (iSCSI), Fibre Channel Protocol (FCP), or Fibre Channel overEthernet (FCoE). The cluster node 204 can present or export data storedon the mass storage devices 208 as logical units (LUNs), for example, tothe host device 202 via interconnects 230-1 through 230-4. In someembodiments, a cluster node 204 can communicate with each other clusternode 204 over the cluster interconnect (not shown), which can beimplement, for example, as a Gigabit Ethernet switch.

In embodiments, the cluster nodes 204 may be configured as highavailability pairs. More specifically, cluster nodes 204-1 and 204-2 maybe paired as high availability pairs and cluster nodes 204-3 and 204-4are paired as high availability pairs. The high availability pairsprovide a redundant failover capability for the storage system 206. Invarious embodiments, each of the cluster nodes 204-1 through 204-4 mayserve information independently of its paired node during normaloperation. However, in the event of individual cluster node 204failures, one or more processes for processing data may transfer fromthe failing or failed cluster node to the surviving paired cluster node.The high availability pair configuration may protect against hardwarefailures, including the failure of network interface cards, and shelfinput/output modules.

In the high availability pair cluster node environment, each node maymonitor the availability status of its partner by means of a heartbeatsignal that may be transmitted between the cluster nodes 204 through theinterconnects 240. In various embodiments, the failure to receive aheartbeat signal over interconnects 240 may indicate the paired clusternode 204 has failed and trigger a failover or takeover event. Inaddition to the heartbeat signal, other information may be communicatedbetween the paired cluster nodes 204 such as, system time, and detailsconcerning temporary disk unavailability due to pending disk firmwareupdates.

FIG. 3 illustrates an exemplary embodiment of hardware architecture of acluster node 300. In some embodiments, cluster node 300 may be the sameor similar as one of the cluster nodes 204 included in the storagesystem 206. Cluster node 300 may include processor 302, memory 304,storage operating system 306, network adapter 308 and storage adapter310. In various embodiments, the components of cluster node 300 maycommunicate with each other via one or more interconnects, such as oneor more traces, buses and/or control lines.

Processor 302 may be one or more of any type of computational element,such as but not limited to, a microprocessor, a processor, centralprocessing unit, digital signal processing unit, dual core processor,mobile device processor, desktop processor, single core processor, asystem-on-chip (SoC) device, complex instruction set computing (CISC)microprocessor, a reduced instruction set (RISC) microprocessor, a verylong instruction word (VLIW) microprocessor, or any other type ofprocessor or processing circuit on a single chip or integrated circuit.In various embodiments, cluster node 300 may include more than oneprocessor.

In one embodiment, cluster node 300 may include a memory unit 304 tocouple to processor 302. Memory unit 304 may be coupled to processor 302via an interconnect, or by a dedicated communications bus betweenprocessor 302 and memory unit 304, which may vary as desired for a givenimplementation. Memory unit 304 may be implemented using anymachine-readable or computer-readable media capable of storing data,including both volatile and non-volatile memory. In some embodiments,the machine-readable or computer-readable medium may include anon-transitory computer-readable storage medium, for example. Theembodiments are not limited in this context.

The memory unit 304 may store data momentarily, temporarily, orpermanently. The memory unit 304 may store instructions and data forcluster node 300. The memory unit 304 may also store temporary variablesor other intermediate information while the processor 302 is executinginstructions. The memory unit 304 is not limited to storing the abovediscussed data; the memory unit 304 may store any type of data. Invarious embodiments, memory 304 may store or include storage operatingsystem 306

In various embodiments, cluster node 300 may include storage operatingsystem 306 to control storage operations on the cluster node 300. Insome embodiments, storage operating system 306 may be stored in memory304 or any other type of storage device, unit, medium, and so forth. Aswill become more apparent with respect to FIG. 3, the storage operatingsystem 306 may implement a write-anywhere file system that cooperateswith virtualization modules to “virtualize” the storage space providedon the storage arrays and storage devices. The file system may logicallyorganize the information as a hierarchical structure of nameddirectories and files on the disks. Each “on-disk” file may beimplemented as set of disk blocks configured to store information, suchas data, whereas the directory may be implemented as a speciallyformatted file in which names and links to other files and directoriesare stored. The virtualization modules allow the file system to furtherlogically organize information as a hierarchical structure of logicaldata blocks on the disks that are exported as logical unit numbers(LUNs).

The network adapter 308 may include the mechanical, electrical andsignaling circuitry needed to connect the cluster node 300 to one ormore hosts and other storage systems over a network, which may include apoint-to-point connection or a shared medium, such as a local areanetwork.

In various embodiments, the storage adapter 310 cooperates with theoperating system 306 executing on the cluster node 300 to accessinformation requested by a host device, guest device, another storagesystem and so forth. The information may be stored on any type ofattached array of writable storage device media such as video tape,optical, DVD, magnetic tape, bubble memory, electronic random accessmemory, micro-electro mechanical and any other similar media adapted tostore information, including data and parity information. Further, thestorage adapter 310 includes input/output (I/O) interface circuitry thatcouples to the disks over an I/O interconnect arrangement, such as aconventional high-performance, FC serial link topology.

FIG. 4 illustrates an example of an operating system 400 which can beused to implement an attached clustered storage system such as thestorage systems and operating system shown in FIGS. 1A, 1B, 2 and 3. Invarious embodiments, operating system 400 may include components,modules, functional segments, and so forth to provide read and writecapabilities to a host device and other storage systems. In addition,operating system 400 may also provide importation capabilities from asource storage system to a target storage system. In this exemplaryembodiment, the operating system 400 is implemented in and discussedfrom the perspective of the target storage system. More specifically,operating system 400 may be implemented on one or more cluster nodes ofthe storage system receiving the information for importation, e.g. atarget storage system. However, various embodiments are not limited inthis manner and the operating system 400 may be implemented on anycontroller, computing system, computing device, processing device,storage system and so forth. Furthermore and as will be discussed inmore detail below, one or more of the components of operating system 400may have an instance or be implemented on every cluster node in astorage system. However other components may only have instances onparticular cluster nodes, such as the cluster node bounded with thesource storage system's source logical unit (source logical unit) andtarget storage system's logical unit (target logical unit).

In the illustrated embodiment the storage operating system implements aSCSI module (S-module 405), and a data module (D-module 450). TheS-module 405 and D-module 450 may be implemented on the same clusternodes, controllers or computing devices. The functional components incombination with underlying processing hardware form the S-module 405and D-module 450. While described as function components or modules ofthe S-module and D-module herein, the functional components or modulescan be logically located essentially any place in the storage operatingsystem.

The S-module 405 and D-module 450 may include multiple functionalcomponents that provide a data path for a host to access informationstored in a logical unit using block access protocols, such as iSCSI,FCP, or FCoE. In addition, the S-module 405 and D-module 450 may includefunctional components or modules to import information from a sourcestorage system and source logical unit to a target storage system andtarget logical unit. Finally, the S-module 405 and D-module 450 mayprovide takeover and giveback capabilities in the high availabilitycluster node environment.

In some embodiments, the S-module 405 may process host device read andwrite requests, mirroring of the write input/outputs from a host deviceto the source storage system during an importation operation, andcheckpointing to provide restart after failure capabilities during animportation operation. In addition, components of the S-module 405 maycontrol various takeover and giveback functionality during a takeover orgiveback event. These and other details will become more apparent in thedescription below.

The functional components in the S-module 405 include an import module410, a transport interface module 420 and a node interface module 422.In various embodiments, the import module 410 may include an import coremodule 412, an import management module 414 and an import interfacemodule 416.

In various embodiments, the import module 410 may enable and controldifferent aspect of the storage system before, during and after theimportation of information from the source storage system to the targetstorage system including during a takeover or giveback event. The sourcestorage system may include a source logical unit and may be the storagesystem having information for importation and the target storage systemmay have a target logical unit and may be the storage system to receivethe information from the source storage system.

In some embodiments, the import module 410 may include an import coremodule 412 to handle input/output requests from a host device or guestdevice while information is being imported from a source storage systemto the target storage system. Further, the import core module 412 mayalso handle processing during a takeover or giveback events whileimporting information from the source storage system to the targetstorage system.

With respect to handling the input/output requests from a host device,the import core module 412 operating on the cluster node bound to thesource logical unit handles the read, write and abort requests when thesource storage system and target system are bound for importation ofinformation. More specifically, the import core module 412 may readinformation from the source logical unit, and write information to boththe source logical unit and the target logical unit based on requestsreceived from a host device. The import core module 412 may sendinformation retrieved from the source logical unit based on the readrequest to the host device, and notify the host device if the readrequest was successfully completed or not successfully completed.

The import core module 412 may also mirror all write requests to boththe source logical unit and target logical unit when information isbeing imported from the source logical to the target logical. Morespecifically, the import core module 412 may write information to boththe source logical unit and the target logical unit on a block-by-blockbasis, chunk basis, and so forth. In some embodiments, the import coremodule 412 may first write the information to the source logical unitbefore writing the information to the target logical unit. Uponcompletion, the import core module 412 may notify the host devicewhether the write request was successfully completed or not.

The import core module 412 may also handle various processing during atakeover or giveback event. More specifically, the import core module412 operating on the cluster node taking over control from anothercluster may receive an event notification that a takeover event isoccurring from the import storage management module 454, as will bediscussed in more detail below. In addition, the import core module 412operating on the cluster node giving back control to another clusternode may receive an event notification that a giveback event isoccurring from the import storage management module 454.

In response to receiving an event notification that a takeover event ora giveback event is occurring, the import core module 412 may suspend orstop all importation processes importing information from the sourcelogical unit to the target logical unit. Further, the import core module412 on the cluster node taking control of processing may initialize andbind any logical units bound to the cluster node losing control to thecluster node gaining control. For example, if the source logical unitand/or the target logical unit is bound to the cluster node losing thecontrol, the import core module 412 may bind one or both of the logicalunits to the cluster node taking control.

In addition, the import core module 412 on the cluster node takingcontrol may also update any configuration and relationship informationin a configuration data store, such as configuration data store 424 andthen restart the importation process from the source logical unit to thetarget logical. The importation process may be restarted from the lastcheckpoint saved in the target logical unit.

The import module 410 may also include an import management module 414to provide import operations between the source storage system and thetarget storage system, and in particular, the source logical unit andthe target logical unit. The import management module 414 may process afull logical unit copy or importation from the source logical unit tothe target logical unit by reading every block of the source logicalunit and writing every block to the target logical unit.

In some embodiments, the import management module 414 may divide thesource logical unit into a set of extents that may further be dividedinto a set of regions. By dividing the source logical unit into regions,an importation operation may be restarted in the event of node failureor reboot by utilizing checkpointing. Once the information is dividedinto regions, the information may be copied or imported on aregion-by-region basis. For the given region being imported, theinformation is read from the source logical unit and written to thetarget logical unit. In some embodiments, the information may be read inunits of 64 kilobytes (KB) chunks within the region because the writeanywhere file system (WAFL) may only allow 64 KB chunk writes at a time.However, various embodiments are not limited in this manner and the WAFLsystem may allow other size chunk writes at a time.

Once an entire extent is copied to the target logical unit, a checkpointis persisted on the target storage system in the configuration datastore to keep track of the current point in the importation process. Thepersistent checkpoint allows the importation process to restart from thelast known successful extent import point in the case of a failure or arestart of the importation process. A failure event may occur when acluster node is restarted or rebooted, a takeover or giveback eventoccurs, on when a volume for the target storage system goes offline, forexample.

During the importation process, the import management module 414 mayalso monitor host write requests and determine if the write request isto the same logical block(s) currently being read from the sourcelogical unit for importation. In this case, the import management module414 may queue the importation read request until the host devices writerequest is completed and the information is written to the sourcelogical unit. The import management module 414 may then read theinformation from the source logical unit at the logical blocks writtento by the host device and import the information to target logical unit.

In a cluster node system, only one instance of the import managementmodule 414 on one of the cluster nodes may operate at one time. Morespecifically, an instance of the import management module 414 mayoperate on the cluster node bound with the source logical unit tocontrol the importation of information from the source logical unit tothe target logical unit. However in some embodiments, the importmanagement module 414 may be operating any of the cluster nodes in acluster node system.

The import module 410 may also include an import interface module 416 toprovide an interface and manage read and write requests between thecomponents of the S-module 405 and the D-module 450. For example, theimport interface module 416 may receive host read and write requestsfrom the import core module 412 and map the request to the appropriatelogical unit to complete the request. In another example, the importinterface module 416 may receive read and write requests from the importmanagement module 414 for the importation of information from the sourcelogical unit to the target logical. The import interface module 416 maythen map the request to the appropriate logical unit to completerequest.

Further the import interface module 416 may maintain and updateinformation to perform file operations with the source logical unit andthe target logical unit. For example, the import interface module 416may manage and control information such as the location of the clusternode and D-module bound to the source logical unit and the targetlogical unit such that any read and write requests are forwarded to thecorrect logical unit during the importation of information.

In addition, the import core module 412 may then use the destinationD-module identification for handling host read and write requests andthe import management module 414 may use the destination D-moduleidentification for handling import read and write requests. Thedestination D-module identification may be maintained in configurationdata store 424 along with other configuration information.

In various embodiments, the import interface module 416 may receive readand write requests from the import core module 412 and the importmanagement module 414 and direct the requests to the appropriate logicalunit to be executed. For example, the import interface module 416 mayreceive a read request to read a source logical unit and the importinterface module 416 may map the request to the correct source logicalunit based on the D-module identification. In another example, theimport interface module 416 may receive a write request to writeinformation to a source logical unit and the import interface module 416may map the write request to the correct source logical unit based onthe D-module identification.

In another example, the import interface module 416 may receive readrequest to read information from the target logical unit and the importinterface module 416 may send the read request to the write anywherefile system layout (WAFL) module 456 to read the information from thetarget logical unit. In a fourth example, the import interface module416 may receive a write request to write information to the targetlogical unit and the import interface module 416 may send the writerequest to the WAFL module 456 to write information to the targetlogical unit.

In some embodiments, S-module 405 may have a transport interface module420 which may include one or more communication components to enablecommunication of commands and data among the modules of storage system,such as to and from the D-module 450. More specifically, the transportinterface module 420 may enable communication of information or datawith the D-module 450, such as functional calls, information or datablocks, or other types of communication messages.

The node interface module 422 may include one or more functionalcomponents to provide various communication capabilities to interfacewith a host device and a source storage system. For example, the nodeinterface module 422 may include components to enable communication overone or more of an Ethernet network or a Fibre Channel (FC) network. Inaddition, the node interface module 422 may enable exchanging blocks, ordiscrete frames or packets of data according various communicationprotocols. In some embodiments, the node interface module 422 mayinclude one or more protocols to manage and enable communication overthe FCP, iSCSI, or FCoE connections to/from the host and/or anotherstorage system.

The S-module 405 may also include or be coupled with a configurationdata store 424 to store configuration and relationship information forthe computer system. The configuration data store 424 may be any filestructure and maintained in one or more storages devices, such as memory304. In some embodiments, the configuration data store 424 maycommunicate information between the import interface module 416 whichmay receive information from other components of the operating system400. However, various embodiments are not limited in and any componentof the operating system 400 may communicate with the configuration datastore 424.

The information may be maintained and updated in the configuration datastore 424 during importation of information, reception of read/writerequests, during failover events, and so forth. Various components andmodules may store and update information in the configuration data store424, such as the D-module identification, a virtual serveridentification, import management identification to identify the importmanagement module location, target logical unit identification, sourcelogical unit identification, import home node identification, importcurrent node identification and import state information. Theconfiguration data store 424 is not limited to storing the above-recitedinformation and may store other information.

As previously discussed, the storage operating system may include aD-module 450 to manage, control and communicate with one or more storagearrays and logical units. For example, the D-module 450 may bind withand communicate with a source logical unit and a target logical unit. Invarious embodiments, the D-module 450 may include a transport interfacemodule 452, an import storage management module 454 and a write anywherefile system layout module 456. While these modules are shown ascomponents of the D-module 450 in this description, they can be locatedlogically at essentially any place in the operating system.

In various embodiments, the transport interface module 452 may be thesame as or similar to transport interface module 420. More specifically,the transport interface module 420 includes one or more communicationcomponents to enable communication of commands and data among themodules of storage system, such as to and from the S-module 405. Morespecifically, the transport interface module 452 may enablecommunication of information or data with the S-module 405, such asfunctional calls, information or data blocks, or other types ofcommunication and information messages.

The D-module 450 may also include an import storage management module454 to provide the components of the operating system, such as theimport module 410, import management module 414 and the import interfacemodule 416 access to the source logical unit and target logical unit.For example, the import storage management module 454 will handle hostdevice read request from the import core module 412 via the importinterface module 416 by reading the information from the source logicalunit. As previously discussed, a host device read request will always beserviced by the source logical unit during the importation operation. Inanother example, the import storage management module 454 may handlehost device write requests from the import core module 412 via theimport interface module 416 by first writing the information to thesource logical unit and then to the target logical unit via the WAFLmodule 456.

The import storage management module 454 may also manage range locks toserialize host device write request with importation write request. Arange lock may limit a host device from accessing a particular region ofinformation while the information is being imported. In someembodiments, the import storage management module 454 may receive arequest for a range lock from the import management module 414 for theregion of information for importation from the source logical unit tothe target logical unit. The import storage management module 454 willhold a range lock, when there are outstanding host device write requestsin the region for importation and will release the range lock upon thecompletion of the host device write requests on both the source logicalunit and the target logical unit.

In various embodiments, the import storage management module 454 mayalso manage high availability notifications from a high availability(HA) subsystem (not shown) and may also handle takeover and givebackevents. When a takeover or giveback event occurs, the import storagemanagement module 454 may receive information from the HA subsystem thatthe event is occurring and notify the appropriate modules of theoperating system 400, such as the import core module 412. The importcore module 412 may initialize or start the takeover or givebackprocess. For example, in response to receiving the notification of theevent the import core module 412 may stop any in progress imports andinitialize the takeover or giveback event.

As will be discussed in more detail below, the import storage managementmodule 454 may be initiated and operate on the cluster node where thesource logical unit resides or is bound to. More specifically, thecluster node where the source logical unit resides may be identified asthe “current home node,” and the import storage management module 454will run on the cluster node identified as the “current home node” suchthat the import storage management module 454 may serialize the hostdevice write request with importation write request for the sourcelogical unit and the target logical unit.

In some embodiments, the D-module 450 may also include a write anywherefile system layout (WAFL) module 456 to communicate with a storagearray, one or more disks, one or more storage devices and so forthincluding the target logical unit. The WAFL module 456 may manage thelayout of information on storage array, disks, storage devices, etc. andserves read and write requests to the target logical unit from the hostdevice and the source storage system. In some embodiments, the WAFLmodule 456 may receive and service read and write requests to the targetlogical unit from the import interface module 416. The WAFL module 456may include storage access protocols such as Small Computer SystemInterface (SCSI) or FCP to communicate information to and from thestorage array, disks, storage devices and so forth.

FIGS. 5A/5B illustrate exemplary embodiments of storage systems in a SANenvironment for conducting importation operations from a source storagesystem and source logical unit to a target storage system and targetlogical unit. FIG. 5A illustrates one such configuration where thesource logical unit 560 and the target logical unit 570 are co-locatedor bound to the same cluster node.

FIG. 5A includes a host device 502 which may be the same or similar ashost devices 102 and 202, interconnects 530-1 through 530-4 connectingthe host device 502 to cluster nodes 504-1 through 504-4, respectively.In various embodiments, cluster nodes 504 may be the same as or similarto cluster nodes 204 and cluster node 300 and may implement one or moreof the components or modules of storage operating system 400.

In some embodiments, the cluster nodes 504-1 through 504-4 may formclustered pairs to provide failover, takeover, and givebackfunctionality. More specifically, in FIG. 5A cluster nodes 504-1 and504-2 are paired as high availability pairs and cluster nodes 504-3 and504-4 are paired as high availability pairs. In various embodiments,each of the cluster nodes 504-1 through 504-4 may serve informationindependently of its paired node during normal operation. However, inthe event of individual cluster node 504 failures, one or more processesfor transferring and importing data may be transferred from the failedcluster node to the surviving paired cluster node over interconnects540. The high availability pair configuration can protect againsthardware failures, including network interface cards and shelfinput/output module failures.

FIG. 5A illustrates clusters nodes 504 having S-modules 505 andD-modules 550 and each of the cluster nodes 504 may include an instanceof an import core module 512. In addition, the cluster node 504-1 boundto the source logical unit 560 may include an instance of the importmanagement module 514 and the import storage management module 554 andthe cluster node 504-1 bound to the target logical unit 570 may includean instance of the WAFL module 565. Any cluster node 504 bound to thesource logical unit 560 will have an instance of the import managementmodule 514 and the import storage management module 554 operating on it.Further, any cluster node 504 bound to the target logical unit 570 willhave an instance of the WAFL module 565 operating on it.

When the source logical unit 560 and the target logical unit 570 areco-located and bound to the same cluster node 504 the path cost betweenthe S-module 505 and the D-module 550 are low and the asymmetric logicalunit access (ALUA) may be reported to the host device 502 as activeoptimized. More specifically, the cluster node 504-1 may reportinterconnect 530-1 as active optimized and all the other interconnectsmay be reported as active non-optimized. The host device 502 may usethis information to communicate information to the storage system. Forexample, the host device 502 may direct read and write requests tocluster node 504-1 over interconnect 530-1.

FIG. 5B illustrates another exemplary embodiment of a storage computingsystem 525 where the source logical unit 560 and the target logical unit570 are not co-located. In this exemplary embodiment, the source logicalunit 560 is bound to cluster node 504-1 and the target cluster node 570is bound to cluster node 504-4. As previously discussed, the importmanagement module 514 and import storage management module 554 will beinitiated and operate on the cluster node bounded to the source logicalunit 560. In this example, the import management module 514 and theimport storage management module 554 are initiated and operate oncluster node 504-1. In addition, the WAFL module 556 is initiated andoperates on the cluster node bound to the target logical unit 570. Inthis example, the WAFL module 556 is initiated and operates on clusternode 504-4.

When the source logical unit 560 and the target logical unit 570 are notco-located the path costs to the cluster node bounded to the targetlogical unit 570 are low and AULA is reported as active optimized to thehost device 502. Thus, in this embodiment, interconnect 530-4 would beidentified as active optimized. All other paths including 530-1 through530-3 would be identified as active non-optimized. In some instances,there may be a performance impact in this configuration because readsand writes between the host device 502, the source logical unit 560 andthe target logical unit 570 will have to traverse additional clusterinterconnects.

FIGS. 6A/6B/6C illustrate exemplary embodiments of storage computingsystems of various importation configurations when a takeover orgiveback event occurs. Computing systems 600, 625 and 650 may be thesame as or similar to computing system 500 and 525 of FIGS. 5A and 5B.

FIG. 6A illustrates a storage computing system 600 having both thesource logical unit 560 and target logical unit 570 co-located andbounded to cluster node 504-1. In this exemplary embodiment, a takeoveror giveback event may occur causing cluster node 504-2 to take controlof the importation operation and be bounded to both the source logicalunit 560 and the target logical 570.

As previously discussed, the import storage management module 552 mayreceive information that an event has occurred, such as a takeover eventor a giveback event. In some embodiments, the importation of informationfrom the source logical unit 560 to the target logical unit 570 may failuntil the event is completed. The import storage management module 552may notify the import core modules 512 of the event and appropriateactions will be taken to complete the event. For example, import coremodule 512 may stop all importation of information until the event iscompleted.

When a takeover event occurs such as when one cluster node takes overimportation and read/write processing from another cluster node becauseof a failure, the import core module 512 on the cluster node 504 takingover the processing may initialize the logical units on the new clusternode 504. For example, in FIG. 6A import core module 512-2 mayinitialize and bind the source logical unit 560 and the target logicalunit 570 to the new cluster node 504-2. In addition, the import coremodule 512-2 may update all the appropriate information in theconfiguration data store to properly configure the storage computingsystem. For example, the import core module 512-2 may update theD-module identification with the new D-module 550-2 and the virtualserver identification, and import current node identification toidentify the new cluster node 504-2.

Further, during the takeover event, the import core module 512-2 mayalso initialize and operate import processing including the importmanagement module 514, the import storage management module 552 and theWAFL module 556 on the new cluster node 504-2. The import core module512-2 may also update information in the configuration data store toreflect these changes as well. For example, the import managementidentification may be updated to identify the import management modulelocation on cluster node 504-2.

Once all the import processes including the import management module514, the import storage management module 552 and the WAFL module 556are initiated and operating on the new cluster node 504-2, the importcore module 512-2 may restart the importation process to importinformation. In addition, the importation process may restart importingdata from the last known checkpoint. As previously discussed, after eachextent is imported to the target logical unit, checkpoint information isstored in the last few logical blocks of the target logical unit. Thus,the import management module 514 may continue the importation processfrom the last full extent copied to the target logical unit based on thecheckpoint information and does not have to restart the importation ofinformation from the beginning

In addition, the takeover process will occur seamlessly andtransparently to the host device 502. More specifically, the hostdevice's 502 read and write request will be queued until the new clusternode 504-2 completely takes over processing and the requests will beproperly handle because the appropriate relationship and configurationinformation is updated in the configuration data store.

In the case of a giveback event where one cluster node 504 gives backcontrol of the read/write request and importation processing to anothercluster node 504, the handover may be similar to a takeover event. Forexample and with respect to FIG. 6A, the import storage managementmodule 552 may receive information from the HA subsystem indicating agiveback event is to occur on. The import storage management module 552may notify the import core module 512 on the cluster node 504 givingback control to another node, import core module 512-1 on cluster node504-1 in this example, of the give back event. The import core module512-1 may stop all importation processing until the giveback event issuccessfully completed. The import core module 512 receiving control maybind the logical units to the new cluster node, initialize processes onthe new cluster node, and update the configuration information in theconfiguration data store. With respect to FIG. 6A, import core module512-2 may bind logical units 560 and 570 to cluster node 504-2. Theimport core module 512-2 may also initialize and operate the importmanagement module 514, import storage management module 552 and the WAFLmodule 556 on cluster node 504-2. In addition, configuration andrelationship information may be updated in the configuration data storeby the import core module 512-2. For example, the import core module512-2 may update the D-module identification with the new D-module 550-2and the virtual server identification, and import current nodeidentification to identify the new cluster node 504-2.

Once all the import processes including the import management module514, the import storage management module 552 and the WAFL module 556are initiated and operating on the new cluster node 504-2, the importcore module 512-2 may restart the importation process to importinformation. In addition, the importation process may restart importingdata from the last known checkpoint, as previously discussed.

FIG. 6B illustrates another exemplary embodiment of a storage system 625when a takeover/giveback event occurs when the logical units are notco-located. In this exemplary embodiment, the cluster node 504-4 boundto the target logical unit 570 loses control to cluster node 504-3either via a takeover or a giveback event. As similarly discussed abovewith respect to FIG. 6A, the import storage management module 552 mayreceive an indication that a takeover or giveback event is occurring oncluster node pairs 504-3 and 504-4 via the HA subsystem. If the event isa takeover event, the import management module 552 may notify the importcore module 512 operating on the cluster node 504 taking over control ofthe event. In this exemplary embodiment, import core module 512-3 oncluster node 504-3 will receive an event notification from the importmanagement module 552 of the takeover event. If the event is a givebackevent, the import management module 512 on the cluster node 504 givingback control will receive the event notification. In this exemplaryembodiments, import module 512-4 on cluster node 504-4 will receive theevent notification for a giveback event.

In either case, the import core module 512 receiving the eventnotification will stop all importation and read/write request processinguntil the event has completed. In addition, the import core module 512receiving or taking control of the import may bind the target logicalunit 570 to the new cluster node, initialize processes on the newcluster node, and update the configuration information in theconfiguration data store. With respect to FIG. 6B, import core module512-3 may bind the target logical unit 570 to cluster node 504-3. Theimport core module 512-3 may also initialize and operate the WAFL module556 on cluster node 504-3. However, the import management module 514 andthe import storage management module 552 will remain operating on thenode bound to the source logical unit 560, cluster node 504-1. In thisexample, the configuration and relationship information may be updatedin the configuration data store by the import core module 512-3.

Once all the import processes including the import management module514, the import storage management module 552 and the WAFL module 556are initiated and operating, the import core module 512-3 may restartthe importation process to import information. In addition, theimportation process may restart importing data from the last knowncheckpoint, as previously discussed.

FIG. 6C illustrates another exemplary embodiment of a storage system 650when a takeover/giveback event occurs when the logical units are notco-located. In this exemplary embodiment, the cluster node 504-1 boundto the source logical unit 560 loses control to cluster node 504-2either via a takeover or a giveback event. As discussed above withrespect to FIGS. 6A and 6B, the import storage management module 552 mayreceive an indication that a takeover or giveback event is occurring oncluster node pairs 504-1 and 504-2 via the HA subsystem. If the event isa takeover event, the import management module 552 may notify the importcore module 512 operating on the cluster node 504 taking over control ofthe event. In this exemplary embodiment, import core module 512-2 oncluster node 504-2 will receive an event notification from the importmanagement module 552 of the takeover event. If the event is a givebackevent, the import management module 512 on the cluster node 504 givingback control will receive the event notification. In this exemplaryembodiments, import module 512-1 on cluster node 504-1 will receive theevent notification.

In either case, the import core module 512 receiving the notificationmay stop all importation and read/write request processing until theevent has completed. In addition, the import core module 512 takingcontrol import may bind the source logical unit 560 to the new clusternode, initialize processes on the new cluster node, and update theconfiguration information in the configuration data store. With respectto FIG. 6C, import core module 512-2 may bind the target logical unit560 to cluster node 504-2. The import core module 512-2 may alsoinitialize and operate the import management module 514 and importstorage management module 552 on cluster node 504-2. However, the WAFLmodule 556 will remain to operate on the node bound to the targetlogical unit 570, cluster node 504-4. In this example, the configurationand relationship information may be updated in the configuration datastore by the import core module 512-2. For example, the import coremodule 512-2 may update the D-module identification with the newD-module 550-2 and the virtual server identification, import home nodeidentification and import current node identification to identify thenew cluster node 504-2.

Once all the import processes including the import management module514, the import storage management module 552 and the WAFL module 556are initiated and operating, the import core module 512-2 may restartthe importation process to import information. In addition, theimportation process may restart importing data from the last knowncheckpoint, as previously discussed.

FIG. 7 illustrates one exemplary embodiment of a logic flow 700 of astorage computing system during a takeover or giveback event. Logic flow700 may be representative of some or all of the operations executed byone or more embodiments described herein.

At block 702, information indicating a takeover or giveback event isoccurring or has occurred may be received by a cluster node of a storagecomputing system, such as computing system 206. More specifically, oneor more processes, such as an import storage management module mayreceive information from a high availability (HA) subsystem that acluster node has failed, one or more interconnects have failed, or acluster node wants to giveback control to another cluster node in thestorage system. Various embodiments are not limited to these examplesand the HA subsystem may detect other failures, errors, and so forth andprovide information that a takeover or giveback event is occurring.

In various embodiments, a takeover or giveback event may be initializedand any importation of information may be paused or stopped until theevent has completed on the storage computing system at block 704. Invarious embodiments, the import storage management module may notify animport core module that event is occurring and the import core modulemay stop the transfer of information from a source logical unit to atarget logical unit. During a takeover event, the import core module onthe cluster node taking over control from another node may receive thenotification and stop the importation of information. However, during agiveback event, the import control module on the cluster node givingcontrol back to another cluster node may stop importation ofinformation.

At logical block 706, any logical units bound to the cluster node losingcontrol may be bound to the new cluster node gaining control. Morespecifically, the source logical unit, the target logical unit, or bothmay be bound to the new cluster node if they are bound to the originalcluster node losing control.

In addition, any processes operating on the cluster node losing controlmay be initiated and operate on the new cluster node at logical block708. For example, the import management module, import storagemanagement module, and WAFL module may be started on the new clusternode taking control if they were operating on the cluster node losingcontrol. Various embodiments are not limited to these modules, anycomponents, modules and processes may be initiated and operate on thenew cluster that was operating on the cluster node losing control.

Configuration and relationship information may be updated to identifythe location of the various processes, to identify the cluster node thelogical units are bound to, and to identify information such that readand write requests are directed to the correct cluster node. Forexample, a D-module identification may be updated in a configurationdata store to the current node bound to the source logical unit and theimport management module. In another example, a current nodeidentification may be updated to the current node bound to the sourcelogical unit such that read and write requests directed to the sourcelogical unit and the import management module. In a third example, animport management identification to identify the import managementmodule location may be updated such that one or more processes andcomponents may be able to locate and direct information to the importmanagement identification module. In addition, import current nodeidentification may be updated to indicate the cluster node where theimport management identification is currently operating on. Otherinformation may also be updated to reflect the change in cluster nodes.

At logical block 712, any importation processes may be restarted andinformation from the source logical unit may be copied to the targetlogical unit. The importation of information may restart from the lastknown checkpoint. As previously discussed, after each extent is importedto the target logical unit, checkpoint information is stored in the lastfew logical blocks of the target logical unit. Thus, the import mayresume or continue from the last full extent copied to the targetlogical unit based on the checkpoint information and does not have torestart the importation of information from the beginning.

FIG. 8 illustrates an exemplary embodiment of logic flow 800. The logicflow 500 may be representative of some or all of the operations executedby one or more embodiments described herein. For example, the logic flow800 may illustrate operations performed by the system 100, system 150,system 200, cluster node 300 and so forth.

In the illustrated embodiment shown in FIG. 8, the logic flow 800 mayinclude receiving an event notification for a pair of cluster nodeshaving a first cluster node and a second cluster node, the eventnotification indicating an occurrence of a takeover event or a givebackevent at block 805. In various embodiments, the event notification maybe generated and based on a failure of either the first cluster node orthe second cluster. However various embodiments are not limited in thismanner the event notification may be based on the first cluster node orthe second cluster node coming back online.

Logic flow 800 may also include suspending copying of information from asource logical unit to a target logical unit at block 810. For example,information on the source logical unit of a source cluster system may becopied or imported to the target logical unit on a target clustersystem. In some embodiments, when an event occurs on a cluster nodebound to either the source logical unit or the target logical unit andevent notification is received, the importation or copying ofinformation may be stopped or suspended.

Further, at block 815 the logic flow 800 may include transferring one ormore processes from the first cluster node to the second cluster node.More specifically, one or more processes for transferring and importingdata may be transferred from the failed cluster node to the survivingpaired cluster node or back to a node coming back online. The logic flow800 may also include resuming importation of information from the sourcelogical unit to the target logical unit at block 820.

FIG. 9 illustrates an embodiment of an exemplary computing architecture900 suitable for implementing various embodiments as previouslydescribed. In one embodiment, the computing architecture 900 may includeor be implemented as part of computing system, such as storage systems106, 152 and 200.

As used in this application, the terms “system” and “component” areintended to refer to a computer-related entity, either hardware, acombination of hardware and software, software, or software inexecution, examples of which are provided by the exemplary computingarchitecture 900. For example, a component can be, but is not limited tobeing, a process running on a processor, a processor, a hard disk drive,multiple storage drives (of optical and/or magnetic storage medium), anobject, an executable, a thread of execution, a program, and/or acomputer. By way of illustration, both an application running on aserver and the server can be a component. One or more components canreside within a process and/or thread of execution, and a component canbe localized on one computer and/or distributed between two or morecomputers. Further, components may be communicatively coupled to eachother by various types of communications media to coordinate operations.The coordination may involve the uni-directional or bi-directionalexchange of information. For instance, the components may communicateinformation in the form of signals communicated over the communicationsmedia. The information can be implemented as signals allocated tovarious signal lines. In such allocations, each message is a signal.Further embodiments, however, may alternatively employ data messages.Such data messages may be sent across various connections. Exemplaryconnections include parallel interfaces, serial interfaces, and businterfaces.

The computing architecture 900 includes various common computingelements, such as one or more processors, multi-core processors,co-processors, memory units, chipsets, controllers, peripherals,interfaces, oscillators, timing devices, video cards, audio cards,multimedia input/output (I/O) components, power supplies, and so forth.The embodiments, however, are not limited to implementation by thecomputing architecture 900.

As shown in FIG. 9, the computing architecture 900 includes a processingunit 904, a system memory 906 and a system bus 908. The processing unit904 can be any of various commercially available processors.

The system bus 908 provides an interface for system componentsincluding, but not limited to, the system memory 906 to the processingunit 904. The system bus 908 can be any of several types of busstructure that may further interconnect to a memory bus (with or withouta memory controller), a peripheral bus, and a local bus using any of avariety of commercially available bus architectures. Interface adaptersmay connect to the system bus 908 via slot architecture. Example slotarchitectures may include without limitation Accelerated Graphics Port(AGP), Card Bus, (Extended) Industry Standard Architecture ((E)ISA),Micro Channel Architecture (MCA), NuBus, Peripheral ComponentInterconnect (Extended) (PCI(X)), PCI Express, Personal Computer MemoryCard International Association (PCMCIA), and the like.

The computing architecture 900 may include or implement various articlesof manufacture. An article of manufacture may include acomputer-readable storage medium to store logic. Examples of acomputer-readable storage medium may include any tangible media capableof storing electronic data, including volatile memory or non-volatilememory, removable or non-removable memory, erasable or non-erasablememory, writeable or re-writeable memory, and so forth. Examples oflogic may include executable computer program instructions implementedusing any suitable type of code, such as source code, compiled code,interpreted code, executable code, static code, dynamic code,object-oriented code, visual code, and the like. Embodiments may also beat least partly implemented as instructions contained in or on anon-transitory computer-readable medium, which may be read and executedby one or more processors to enable performance of the operationsdescribed herein.

The system memory 906 may include various types of computer-readablestorage media in the form of one or more higher speed memory units, suchas read-only memory (ROM), random-access memory (RAM), dynamic RAM(DRAM), Double-Data-Rate DRAM (DDRAM), synchronous DRAM (SDRAM), staticRAM (SRAM), programmable ROM (PROM), erasable programmable ROM (EPROM),electrically erasable programmable ROM (EEPROM), flash memory, polymermemory such as ferroelectric polymer memory, ovonic memory, phase changeor ferroelectric memory, silicon-oxide-nitride-oxide-silicon (SONOS)memory, magnetic or optical cards, an array of devices such as RedundantArray of Independent Disks (RAID) drives, solid state memory devices(e.g., USB memory, solid state drives (SSD) and any other type ofstorage media suitable for storing information. In the illustratedembodiment shown in FIG. 9, the system memory 906 can includenon-volatile memory 910 and/or volatile memory 912. A basic input/outputsystem (BIOS) can be stored in the non-volatile memory 910.

The computer 902 may include various types of computer-readable storagemedia in the form of one or more lower speed memory units, including aninternal (or external) hard disk drive (HDD) 914, a magnetic floppy diskdrive (FDD) 916 to read from or write to a removable magnetic disk 918,and an optical disk drive 920 to read from or write to a removableoptical disk 922 (e.g., a CD-ROM or DVD). The HDD 914, FDD 916 andoptical disk drive 920 can be connected to the system bus 908 by a HDDinterface 924, an FDD interface 926 and an optical drive interface 928,respectively. The HDD interface 924 for external drive implementationscan include at least one or both of Universal Serial Bus (USB) and IEEE1394 interface technologies.

The drives and associated computer-readable media provide volatileand/or nonvolatile storage of data, data structures, computer-executableinstructions, and so forth. For example, a number of program modules canbe stored in the drives and memory units 910, 912, including anoperating system 930, one or more application programs 932, otherprogram modules 934, and program data 936. In one embodiment, the one ormore application programs 932, other program modules 934, and programdata 936 can include, for example, the various applications and/orcomponents of the system 100.

A user can enter commands and information into the computer 902 throughone or more wire/wireless input devices, for example, a keyboard 938 anda pointing device, such as a mouse 940. Other input devices may includemicrophones, infra-red (IR) remote controls, radio-frequency (RF) remotecontrols, game pads, stylus pens, card readers, dongles, finger printreaders, gloves, graphics tablets, joysticks, keyboards, retina readers,touch screens (e.g., capacitive, resistive, etc.), trackballs,trackpads, sensors, styluses, and the like. These and other inputdevices are often connected to the processing unit 904 through an inputdevice interface 942 that is coupled to the system bus 908, but can beconnected by other interfaces such as a parallel port, IEEE 1394 serialport, a game port, a USB port, an IR interface, and so forth

A monitor 944 or other type of display device is also connected to thesystem bus 908 via an interface, such as a video adaptor 946. Themonitor 944 may be internal or external to the computer 902. In additionto the monitor 944, a computer typically includes other peripheraloutput devices, such as speakers, printers, and so forth.

The computer 902 may operate in a networked environment using logicalconnections via wire and/or wireless communications to one or moreremote computers, such as a remote computer 948. The remote computer 948can be a workstation, a server computer, a router, a personal computer,portable computer, microprocessor-based entertainment appliance, a peerdevice or other common network node, and typically includes many or allof the elements described relative to the computer 902, although, forpurposes of brevity, only a memory/storage device 950 is illustrated.The logical connections depicted include wire/wireless connectivity to alocal area network (LAN) 952 and/or larger networks, for example, a widearea network (WAN) 954. Such LAN and WAN networking environments arecommonplace in offices and companies, and facilitate enterprise-widecomputer networks, such as intranets, all of which may connect to aglobal communications network, for example, the Internet.

When used in a LAN networking environment, the computer 902 is connectedto the LAN 952 through a wire and/or wireless communication networkinterface or adaptor 956. The adaptor 956 can facilitate wire and/orwireless communications to the LAN 952, which may also include awireless access point disposed thereon for communicating with thewireless functionality of the adaptor 956.

When used in a WAN networking environment, the computer 902 can includea modem 958, or is connected to a communications server on the WAN 954,or has other means for establishing communications over the WAN 954,such as by way of the Internet. The modem 958, which can be internal orexternal and a wire and/or wireless device, connects to the system bus908 via the input device interface 942. In a networked environment,program modules depicted relative to the computer 902, or portionsthereof, can be stored in the remote memory/storage device 950. It willbe appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computerscan be used.

The computer 902 is operable to communicate with wire and wirelessdevices or entities using the IEEE 902 family of standards, such aswireless devices operatively disposed in wireless communication (e.g.,IEEE 902.11 over-the-air modulation techniques). This includes at leastWi-Fi (or Wireless Fidelity), WiMax, and Bluetooth™ wirelesstechnologies, among others. Thus, the communication can be a predefinedstructure as with a conventional network or simply an ad hoccommunication between at least two devices. Wi-Fi networks use radiotechnologies called IEEE 902.11x (a, b, g, n, etc.) to provide secure,reliable, fast wireless connectivity. A Wi-Fi network can be used toconnect computers to each other, to the Internet, and to wire networks(which use IEEE 902.3-related media and functions).

The various elements of the storage systems 106, 152, and 200 aspreviously described with reference to FIGS. 1-6 may include varioushardware elements, software elements, or a combination of both. Examplesof hardware elements may include devices, logic devices, components,processors, microprocessors, circuits, processors, circuit elements(e.g., transistors, resistors, capacitors, inductors, and so forth),integrated circuits, application specific integrated circuits (ASIC),programmable logic devices (PLD), digital signal processors (DSP), fieldprogrammable gate array (FPGA), memory units, logic gates, registers,semiconductor device, chips, microchips, chip sets, and so forth.Examples of software elements may include software components, programs,applications, computer programs, application programs, system programs,software development programs, machine programs, operating systemsoftware, middleware, firmware, software modules, routines, subroutines,functions, methods, procedures, software interfaces, application programinterfaces (API), instruction sets, computing code, computer code, codesegments, computer code segments, words, values, symbols, or anycombination thereof. However, determining whether an embodiment isimplemented using hardware elements and/or software elements may vary inaccordance with any number of factors, such as desired computationalrate, power levels, heat tolerances, processing cycle budget, input datarates, output data rates, memory resources, data bus speeds and otherdesign or performance constraints, as desired for a givenimplementation.

Some embodiments may be described using the expression “one embodiment”or “an embodiment” along with their derivatives. These terms mean that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment. Theappearances of the phrase “in one embodiment” in various places in thespecification are not necessarily all referring to the same embodiment.Further, some embodiments may be described using the expression“coupled” and “connected” along with their derivatives. These terms arenot necessarily intended as synonyms for each other. For example, someembodiments may be described using the terms “connected” and/or“coupled” to indicate that two or more elements are in direct physicalor electrical contact with each other. The term “coupled,” however, mayalso mean that two or more elements are not in direct contact with eachother, but yet still co-operate or interact with each other.

It is emphasized that the Abstract of the Disclosure is provided toallow a reader to quickly ascertain the nature of the technicaldisclosure. It is submitted with the understanding that it will not beused to interpret or limit the scope or meaning of the claims. Inaddition, in the foregoing Detailed Description, it can be seen thatvarious features are grouped together in a single embodiment for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the claimedembodiments require more features than are expressly recited in eachclaim. Rather, as the following claims reflect, inventive subject matterlies in less than all features of a single disclosed embodiment. Thusthe following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment. In the appended claims, the terms “including” and “in which”are used as the plain-English equivalents of the respective terms“comprising” and “wherein,” respectively. Moreover, the terms “first,”“second,” “third,” and so forth, are used merely as labels, and are notintended to impose numerical requirements on their objects.

What has been described above includes examples of the disclosedarchitecture. It is, of course, not possible to describe everyconceivable combination of components and/or methodologies, but one ofordinary skill in the art may recognize that many further combinationsand permutations are possible. Accordingly, the novel architecture isintended to embrace all such alterations, modifications and variationsthat fall within the spirit and scope of the appended claims.

What is claimed is:
 1. A computer-implemented method, comprising:receiving an event notification for a pair of cluster nodes having afirst cluster node and a second cluster node, the event notificationindicating an occurrence of a takeover event or a giveback event;suspending copying of information from a source logical unit to a targetlogical unit; transferring one or more processes from the first clusternode to the second cluster node; and resuming importation of informationfrom the source logical unit to the target logical unit.
 2. Thecomputer-implemented method of claim 1, comprising: associating thesource logical unit, the target logical unit or both with the secondcluster node prior to resuming importation of information.
 3. Thecomputer-implemented method of claim 1, comprising: updatingconfiguration information in a configuration data store to identify thesecond cluster node as the current cluster node for importationprocessing prior to resuming importation of information.
 4. Thecomputer-implemented method of claim 1, comprising: updatingconfiguration information in a configuration data store to identify theone or more processes operating on the second cluster node.
 5. Thecomputer-implemented method of claim 1, the event notificationindicating the second cluster node is taking over processing from thefirst cluster node.
 6. The computer-implemented method of claim 1, theevent notification indicating the first cluster node is giving backprocessing to the second cluster node.
 7. The computer-implementedmethod of claim 1, the resuming comprising resuming from a checkpointidentifying a last extent imported to the target logical unit.
 8. Thecomputer-implemented method of claim 7, the checkpoint stored in aconfiguration data store on a target storage system.
 9. An articlecomprising a computer-readable storage medium comprising a plurality ofinstructions that when executed enable processing circuitry to: receivean event notification for a pair of cluster nodes having a first clusternode and a second cluster node, the event notification indicating anoccurrence of a takeover event or a giveback event; suspend copying ofinformation from a source logical unit to a target logical unit;transfer one or more processes from the first cluster node to the secondcluster node; and resume importation of information from the sourcelogical unit to the target logical unit.
 10. The storage medium of claim9, comprising instructions that when executed enable the processingcircuitry to: associate the source logical unit, the target logical unitor both with the second cluster node prior to resuming importation ofinformation.
 11. The storage medium of claim 9, comprising instructionsthat when executed enable the processing circuitry to: updateconfiguration information in memory to identify the second cluster nodeas the current cluster node for importation processing prior to resumingimportation of information.
 12. The storage medium of claim 9,comprising instructions that when executed enable the processingcircuitry to: update configuration information in memory to identify theone or more processes operating on the second cluster node.
 13. Thestorage medium of claim 9, the event notification indicating the secondcluster node is taking over processing from the first cluster node. 14.The storage medium of claim 9, the event notification indicating thefirst cluster node is giving back processing to the second cluster node.15. The storage medium of claim 9, comprising instructions that whenexecuted enable the processing circuitry to: resume from a checkpointidentifying a last extent imported to the target logical unit.
 16. Thestorage medium of claim 15, the checkpoint stored in a configurationdata store on a target storage system.
 17. An apparatus, comprising:processing circuitry; and logic, at least a portion of which is inhardware, the logic to: receive an event notification for a pair ofcluster nodes having a first cluster node and a second cluster node, theevent notification indicating an occurrence of a takeover event or agiveback event; suspend copying of information from a source logicalunit to a target logical unit; transfer one or more processes from thefirst cluster node to the second cluster node; and resume importation ofinformation from the source logical unit to the target logical unit. 18.The apparatus of claim 17, the logic to associate the source logicalunit, the target logical unit or both with the second cluster node priorto resuming importation of information.
 19. The apparatus of claim 17,the logic to update configuration information in memory to identify thesecond cluster node as the current cluster node for importationprocessing prior to resuming importation of information.
 20. Theapparatus of claim 17, the logic to update configuration information inmemory to identify the one or more processes operating on the secondcluster node.
 21. The apparatus of claim 17, the event notificationindicating the second cluster node is taking over processing from thefirst cluster node.
 22. The apparatus of claim 17, the eventnotification indicating the first cluster node is giving back processingto the second cluster node.
 23. The apparatus of claim 17, the logic toresume from a checkpoint identifying a last extent imported to thetarget logical unit.
 24. The apparatus of claim 23, the checkpointstored in a configuration data store on a target storage system.